From patchwork Thu Apr 30 12:22:22 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Tzvetomir Stoyanov (VMware)" X-Patchwork-Id: 11520165 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0321B1392 for ; Thu, 30 Apr 2020 12:22:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E07A22078D for ; Thu, 30 Apr 2020 12:22:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="LXGR+CJb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726781AbgD3MWd (ORCPT ); Thu, 30 Apr 2020 08:22:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40854 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-FAIL-OK-FAIL) by vger.kernel.org with ESMTP id S1726500AbgD3MWd (ORCPT ); Thu, 30 Apr 2020 08:22:33 -0400 Received: from mail-lj1-x242.google.com (mail-lj1-x242.google.com [IPv6:2a00:1450:4864:20::242]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 22D36C035494 for ; Thu, 30 Apr 2020 05:22:33 -0700 (PDT) Received: by mail-lj1-x242.google.com with SMTP id b2so6255027ljp.4 for ; Thu, 30 Apr 2020 05:22:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=1Wdph4dvvQ7ZWMW79jnjXB5svR+IBQaXspcv5zle/SY=; b=LXGR+CJb9D56bLfI3HBbmrAkd3myfcKmziC2v9bCgDHaGsw/bGenvTiOvKpncvQ7v2 pLAl9dEFkTQWkiiNk3CW9HYLl5tsHbQq2M2U06mllBIOUT5Zon2Fu82vLCH+bUrDzqHX SoFnCmA8R2QCjLJs15/zhoCQT6Tb4WSoNRL1lbofombDHY2El4r47ywe7nP5o1B2L2eK wQPHf4icTwVRZFnWNEw1bivtD3/GX8MTf35+MYzvuooyqdXQ6VxAnN/X7aXKznvxXuZa u7gcKulnloZXmzf+KlZiOTWDDmhrB1DIZ8Nz0LJ+mnPCpdIM2M4i+zwMMR2s5droEtu6 IYDg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=1Wdph4dvvQ7ZWMW79jnjXB5svR+IBQaXspcv5zle/SY=; b=huuSjA7Fr/d0av2h+sL0zX7XngfAcxAy3GdePanmmwJRe2d7o28l5mSdm8n38uTEDr DuCg0znQ0rAdBBfCep/+z07K+dCyQ56zg/8PShQQJxliltZSEUBwOcmOLh7XJ99RUHUE IG9LXTeSo4KGkkcPRuIRz5fXphZ01pIdyBn34WPnwDcnD9SFkmCw6DPrm2yJkKFJF+Jd p8K1Wr9kkQr0LOLAuy8RSXG1TbIqoZbwY5yM2yKAX537sRDQZv8uv8r6mqrS/DwarpVu wqmmjCHKrlehyOwUfxHVhrxPVU/PzeFCRGb6xjrvmbYxbDwKeelYr7XMpcz7xIMozd/c wtMw== X-Gm-Message-State: AGi0PuZFbeF6lkJKv6i6aDrNvDj2p+aDs4IFzCe5hr+4oO+E6sJvsIRI MTnbv2wO1WBqIVw5qdHc4t0= X-Google-Smtp-Source: APiQypLVevHvwNhOjb4dx8GrLuDk4Ut3E72FyMLzUUODvqVeRoLQcOLD1lCK2ezdPPMvSCEc7U2pgw== X-Received: by 2002:a2e:99cc:: with SMTP id l12mr2111400ljj.290.1588249351529; Thu, 30 Apr 2020 05:22:31 -0700 (PDT) Received: from oberon.zico.biz ([83.222.187.186]) by smtp.gmail.com with ESMTPSA id a26sm4793168lfl.66.2020.04.30.05.22.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 30 Apr 2020 05:22:30 -0700 (PDT) From: "Tzvetomir Stoyanov (VMware)" To: rostedt@goodmis.org Cc: linux-trace-devel@vger.kernel.org Subject: [PATCH 4/4] trace-cmd: Do not try to update parent's memory from a fork()-ed child Date: Thu, 30 Apr 2020 15:22:22 +0300 Message-Id: <20200430122222.101276-5-tz.stoyanov@gmail.com> X-Mailer: git-send-email 2.25.4 In-Reply-To: <20200430122222.101276-1-tz.stoyanov@gmail.com> References: <20200430122222.101276-1-tz.stoyanov@gmail.com> MIME-Version: 1.0 Sender: linux-trace-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org When trace-cmd runs a command, specified with the "-F" flag, it forks a child process and executes the command in its context. This child process receives a full copy of the parents memory at the moment of fork(). When it modifies this copy, the parent memory is not affected. Calling the function update_task_filter() in the child context will operate on a valid data, but will not update anything in the parent's databases. Signed-off-by: Tzvetomir Stoyanov (VMware) --- tracecmd/trace-record.c | 34 +++++++++++++++++++++++++++++----- 1 file changed, 29 insertions(+), 5 deletions(-) diff --git a/tracecmd/trace-record.c b/tracecmd/trace-record.c index 1e4d38fa..2b5cd42a 100644 --- a/tracecmd/trace-record.c +++ b/tracecmd/trace-record.c @@ -11,6 +11,7 @@ #include #include #include +#include #include #include #include @@ -1487,18 +1488,35 @@ static int change_user(const char *user) return 0; } +#define TRACE_RUN_SEM "trace_cmd_semaphore_run" +#define TRACE_INIT_SEM "trace_cmd_semaphore_init" static void run_cmd(enum trace_type type, const char *user, int argc, char **argv) { + sem_t *sem_init; + sem_t *sem_run; int status; int pid; + sem_init = sem_open(TRACE_INIT_SEM, O_CREAT, S_IRUSR|S_IWUSR, 0); + if (sem_init == SEM_FAILED) + die("failed to init trace_cmd init semaphore"); + + sem_run = sem_open(TRACE_RUN_SEM, O_CREAT, S_IRUSR|S_IWUSR, 0); + if (sem_run == SEM_FAILED) { + sem_close(sem_init); + sem_unlink(TRACE_INIT_SEM); + die("failed to init trace_cmd run semaphore"); + } + if ((pid = fork()) < 0) die("failed to fork"); if (!pid) { /* child */ - update_task_filter(); + sem_wait(sem_init); tracecmd_enable_tracing(); enable_ptrace(); + sem_post(sem_run); + /* * If we are using stderr for stdout, switch * it back to the saved stdout for the code we run. @@ -1519,11 +1537,17 @@ static void run_cmd(enum trace_type type, const char *user, int argc, char **arg die("Failed to exec %s", argv[0]); } } - if (do_ptrace) { - add_filter_pid(pid, 0); - ptrace_attach(pid); + update_task_filter(); + sem_post(sem_init); + sem_wait(sem_run); + sem_close(sem_init); + sem_unlink(TRACE_INIT_SEM); + sem_close(sem_run); + sem_unlink(TRACE_RUN_SEM); + + if (do_ptrace) ptrace_wait(type); - } else + else trace_waitpid(type, pid, &status, 0); }